Abstract:
Recent developments in cavity enhancement [1] and multiheterodyne
detection [2] of ultrafast nonlinear signals using optical frequency
combs are poised to enable broadband, high-resolution and highly
sensitive 2D IR spectroscopy of gas-phase samples. In 2D IR spectroscopy
of coupled vibrational modes diagonal or off-diagonal peaks can be
suppressed with specific polarization conditions [3]. In the gas phase
molecules rotate freely and rotational eigenstates produce new diagonal
and off-diagonal peaks. Here, we present simulations of gas-phase
rotationally-resolved spectra of the nu3 mode of methyl chloride and the
vibrational mode of carbon monoxide and demonstrate how rotational-state
patterns can be controlled using polarization. Presented polarization
conditions will help mitigate spectral congestion and enable new
applications in studying complex mixtures of gas-phase samples.
[1] Allison, T. K. Cavity-enhanced ultrafast two-dimensional
spectroscopy using higher order modes. J. Phys. B: At., Mol. Opt. Phys.
50, 044004 (2017)
[2] Lomsadze, B. & Cundiff, S. T. Frequency combs enable rapid and
high-resolution multidimensional coherent spectroscopy. Science 357,
1389–1391 (2017).
[3] Zanni, M. T., Ge, N.-H., Kim, Y. S., Hochstrasser, R. M.
Two-dimensional IR spectroscopy can be designed to eliminate the
diagonal peaks and expose only the crosspeaks needed for structure
determination. Proc. Natl. Acad. Sci. 98, 11265–11270 (2001).